Journal of Medical Genetics最新文献

Biallelic variants in NUP107 cause isolated or syndromic steroid-resistant nephrotic syndrome (SRNS), characterised by proteinuria, hypoalbuminaemia and focal segmental glomerulosclerosis that progresses to end-stage renal disease. Patients with syndromic SRNS have microcephaly, developmental delay or intellectual disability and short stature. Simplified gyration is observed in some individuals. We report on a 2-year-old girl with novel biallelic NUP107 variants, c.2606G>T; p.(Gly869Val) and c.1576+1G>A, proteinuria and a severe neurodevelopmental disorder with microcephaly, developmental delay, early-onset seizures, sensorineural hearing loss and brain structural anomalies, including simplified gyral pattern and hypoplasia of the corpus callosum, pons, brainstem and cerebellum. NUP107 is part of the NUP107-160 complex, which, together with other proteins termed nucleoporins, forms the nuclear pore complex (NPC). The NPC regulates nucleocytoplasmic transport and other cellular processes. In patient-derived fibroblasts, we identified aberrantly spliced NUP107 mRNAs with a frameshift and premature stop codon leading to non-sense-mediated mRNA decay, reduced levels of NUP107 transcripts, reduced NUP107 and NUP133 proteins, and a reduced NPC number. In addition, an abnormal nucleolar morphology was found in patient-derived cells. Our functional data support the conclusion that the NUP107 variants underlie the patient's phenotype, thereby broadening the clinical spectrum associated with NUP107 variants to include abnormal brain development.

We analysed rare variants in the non-coding RNU4-2 gene as a potential cause of neurodevelopmental disorder (NDD) and intellectual disability (ID) in a large cohort of individuals enriched for parental consanguinity.Genome sequencing (GS) data from 22 928 individuals in our Biodatabank were queried for rare, monoallelic variants in RNU4-2 From these, 4918 patients presented with NDD/ID. Human Phenotype Ontology (HPO)-encoded clinical information was extracted and analysed using the ontologyX R package.Nearly 50% of the 4918 patients with NDD/ID reported parental consanguinity. Eight relevant heterozygous RNU4-2 variants were identified in 28 patients. n.64_65insT was the most frequently detected variant (20 patients, 71%), while the remaining variants were found in 1 or 2 patients each (n.65A>G, n.66A>G, n.67A>G, n.70T>C, n.76C>T, n.95C>G and n.135A>C). Four variants are novel or ultra-rare, and two of them are in the 3' stem loops. HPO-based analysis revealed a consistent syndromic phenotype characterised by NDD, abnormal brain morphology, hypotonia, global developmental delay, microcephaly, seizures, atypical behaviour and facial dysmorphism. RNU4-2 variants accounted for approximately 0.55% of NDD/ID cases in our full cohort, and 0.25% in the subset of consanguineous patients (all genetic causes included).This study underscores the significance of RNU4-2 as a major genetic cause of NDD/ID, extending its relevance to consanguineous patients, where recessive disorders are often suspected. We advocate for the re-evaluation of existing GS data to uncover potential diagnoses and emphasise the importance of GS as a first-tier diagnostic test.

Background: The management of women with germline pathogenic variants (GPVs) in breast (BC) and ovarian cancer (OC) susceptibility genes is focused on surveillance and risk-reducing surgery/medication. Most women are assigned an average range of risk and treated accordingly, but it is possible to personalise this. Here, we explore the economic impact of risk personalisation.

Method: We compared two strategies for risk stratification for female participants: conventional risk assessment (CRA), which only involves information from genetic testing and personalised risk assessment (PRA), using genetic and non-genetic risk modifiers. Three different versions of PRA were compared, which were combinations of polygenic risk score and questionnaire-based factors. A patient-level Markov model was designed to estimate the overall National Health Service cost and quality-adjusted life years (QALYs) after risk assessment. Results were given for 20 different groups of women based on their GPV status and family history.

Results: Across the 20 scenarios, the results showed that PRA was cost-effective compared with CRA using a £20 000 per QALY threshold in women with a GPV in PALB2 who have OC or BC+OC family history, and women with a GPV in ATM, CHEK2, RAD51C or RAD51D. For women with a GPV in BRCA1 or BRCA2, women with no pathogenic variant and women with a GPV in PALB2 who have unknown family history or BC family history, CRA was more cost-effective. PRA was cost-effective compared with CRA in specific situations predominantly associated with moderate-risk BC GPVs (RAD51C/RAD51D/CHEK2/ATM), while CRA was cost-effective compared with PRA predominantly with high-risk BC GPVs (BRCA1/BRCA2/PALB2).

Conclusion: PRA was cost-effective in specific situations compared with CRA in the UK for assessment of women with or without GPVs in BC and OC susceptibility genes.

A query was sent to the cancer predisposition gene variant database Cancer Variant Interpretation Group UK, on the nonsense variant in NM_032043.3(BRIP1):c.2392C>T,p.(Arg798Ter). The submitter classified this as a variant of uncertain significance, providing very strong variant effect evidence with the intention of adding supporting pedigree information, according to the guidelines used for classification. However, the relatively high population frequency in the UKB cohort of 367/439 920 (0.083%) was a concern as it is higher than expected for the disease frequency, which would reduce the predicted pathogenicity score. This situation highlights the increasing concerns over the use of population data in pathogenicity classification of truncating/loss-of-function (LoF) variants in known cancer predisposition genes, particularly since the addition of UKB control data. Here, we have conducted a series of case-control comparisons for common truncating variants in known breast/ovarian cancer-associated genes, as well as LZTR1-related schwannomatosis, to address this issue using our Manchester cancer screening population compared with controls in UKB data.Our data show strong ORs for these common truncating variants. We propose that for truncating variants in cancer susceptibility genes with a significant case-control OR, apparently conflicting population frequency evidence criteria should be avoided.

Background: The LSM1 gene encodes a subunit of the conserved LSM1-7 protein complex involved in messenger RNA (mRNA) metabolism. Variants in the LSM1 gene have been described in two separate case reports. The first published report identified the homozygous splice-site variant c.231+4A>C, while the second reported a homozygous missense variant. Nevertheless, variation in LSM1 has yet to be established as disease-causing in humans.

Methods: Through exome sequencing and detailed phenotyping, we report six syndromic paediatric patients with the homozygous c.231+4A>C variant in the LSM1 gene, collected via GeneMatcher. GestaltMatcher was used to analyse facial feature similarity, and real-time quantitative PCR (RT-qPCR) confirmed the splice defect caused by the variant. Haplotype analysis assessed whether this variant resulted from independent occurrences or a common ancestral haplotype.

Results: Patients presented with dysmorphic facial features, developmental delay and multisystemic involvement, including urological, cardiac and skeletal manifestations, showcasing the phenotypic spectrum of this syndrome. RT-qPCR confirmed that the c.231+4A>C variant causes exon 3 skipping, producing negligible wild-type LSM1 mRNA expression. Elevated mutant isoform expression confirmed pathogenicity according to the American College of Medical Genetics and Genomics (ACMG) guidelines. We identified this variant in the Muslim Arab and Ashkenazi Jewish populations and determined that it represents a hotspot variant through haplotype analysis.

Conclusion: Our findings establish LSM1, and specifically the c.231+4A>C homozygous variant, as causative for a novel autosomal recessive syndromic neurodevelopmental disorder. These results expand the understanding of LSM1-related diseases and provide a foundation for further investigation of its molecular mechanisms.

Purpose: Facioscapulohumeral muscular dystrophy (FSHD) is a genetic disorder caused by contraction or hypomethylation of the D4Z4 repeat array located at chromosome 4q35. For the disease to manifest, a permissive haplotype is required, as it enables the pathogenic expression of the DUX4 gene. FSHD cases often involve complex rearrangements, such as intrachromosomal rearrangements and translocations, which complicate diagnosis using conventional methods. This study focuses on evaluating the diagnostic potential of single molecule optical mapping (SMOM) for FSHD with complex rearrangements, particularly in cases involving 4q-10q translocations, which present challenges for detection by SMOM alone. Furthermore, we propose an integrated diagnostic strategy, combining SMOM with complementary methods, to improve accuracy in these challenging cases.

Methods: We reviewed the test results of 238 patients with suspected FSHD, and 25 participants with presumed complex rearrangements were included in this study. SMOM was performed on these participants, and the results were manually reviewed and compared with those obtained from Southern blot (SB) analysis.

Results: Nine patients carrying 4q-10q translocation exhibited discrepancies between the two methods. Linear regression analysis revealed a significant discrepancy in chromosomal assignment between SB and SMOM in cases suspected of translocation.

Conclusions: Given the complex nature of FSHD, none of the current methods can independently provide a definitive diagnosis. As misdiagnosis may occur when relying on a single technique, we propose an integrated diagnostic approach, with SMOM as the first-line test.

Background: The microtubule actin crosslinking factor 1 (MACF1) gene encodes microtubule-microfilament cross-linking factor 1 that plays an essential role in the embryonic brain development. MACF1 variants were associated with lissencephaly-9 (LIS9). However, the MACF1-epilepsy relationship was unknown.

Methods: Trios-based whole-exome sequencing was performed on a cohort with generalised epilepsy from the China Epilepsy Gene 1.0 project. The spatial-temporal expression, single-cell sequencing and genotype-phenotype correlation were analysed to explore the role of MACF1 in epilepsy and neurodevelopment.

Results: Two de novo heterozygous and eight biallelic MACF1 variants were identified in 10 unrelated patients. The variants presented significantly high excess by multiple statistical analyses. All patients were diagnosed with generalised epilepsy, among whom three patients presented with neurodevelopmental delay. MACF1 was expressed throughout the lifespan, with three major peaks in the fetal, early childhood and adulthood stages, consistent with seizure onset ages of the patients. The highest expression in adulthood was in the thalamus nucleus, potentially associated with the pathogenesis of generalised epilepsy. The single-cell sequencing in organoids showed MACF1 is widely expressed in the developing brain, especially in the early stage, suggesting a vital role in neurodevelopment. Genotype-phenotype association analysis revealed that LIS9-associated variants were featured by de novo monoallelic variants clustered within the C-terminal; the autism spectrum disorder-associated variants were mainly de novo monoallelic variants located at the spectrin-repeat rod domains. In contrast, the epilepsy-associated variants were biallelic missense variants, and those in the plakin domain were potentially associated with neurodevelopment delay.

Significance: MACF1 is potentially a novel causative gene of generalised epilepsy.

Background: Scoliosis is the most common paediatric spinal deformity. More than 80% of scoliosis is idiopathic and appears during the adolescent growth spurt. Spinal fusion surgery is often required for patients with progressive adolescent idiopathic scoliosis (AIS), and the genetic risk factors for severe disease (defined here as curve >35 degrees) are largely unknown.

Methods: To explore the role of rare variants in severe AIS, exome sequence data from 1221 individuals with AIS were compared with both 1397 in-house European ancestry controls and 56885 gnomAD non-Finish European controls. Segregation analysis of variants in prioritised genes was performed in additional family members. A replication study was performed using the Geisinger MyCode cohort. FNDC1 function was investigated in fndc1 null mutant zebrafish.

Results: Rare variants were enriched in 84 genes, including RAF1 (Noonan syndrome), FBN1 (Marfan syndrome) and FNDC1, in individuals with severe AIS. FNDC1, which had previously been associated with joint hypermobility, harboured missense variants in 4.0% of individuals with AIS compared with 2.3% of controls (p=0.00764, OR=1.78). FNDC1 variants segregated with AIS in five multiplex families with incomplete penetrance. In addition, FNDC1 rare variants were also associated with scoliosis in the Geisinger MyCode cohort (p=0.0002, OR=3.6). Disruption of the fndc1 locus in zebrafish resulted in increased bone mineral density.

Conclusion: We broadened the phenotype associated with RAF1 and FBN1 variants and identified FNDC1 as a novel gene associated with severe AIS. Mechanistic alterations of bone mineral density or joint hypermobility may explain the association of FNDC1 missense variants with AIS.